Production of orthophenylphenols

ABSTRACT

The present invention relates to a process for the preparation of orthophenylphenol and derivatives thereof, specifically by the reaction of dibenzofuran and its derivatives with hydrogen, at elevated temperatures, in the presence of a catalyst comprised of one or more Group VIII elements.

BACKGROUND OF THE INVENTION

This invention relates to a process for the preparation of orthophenylphenol and its derivatives. More particularly, it relates to a process for the reaction of dibenzofuran and its derivatives with hydrogen, at elevated temperatures, in the presence of a catalyst comprised of one or more Group VIII elements.

Dibenzofuran may be represented by the following formula numbered according to Chemical Abstracts (1973) ##SPC1##

Under the influence of a catalyst a hydrogenolysis reaction takes place, whereby one of the two carbon-oxygen bonds of the furan structure in dibenzofuran may be cleaved with the subsequent addition of hydrogen to each of these sites, for example, the bond between the numbered members (5) and (5a) or (5) and (4a) may be cleaved with subsequent addition of hydrogen to form orthophenylphenol product.

It will, therefore, be understood that derivatives of dibenzofuran used in this process of the present invention for preparing derivatives of orthophenylphenol should include a heterocyclic ring of at least five members with oxygen being the hetero atom, and the ring thereof containing unsaturation at each of the carbon atoms attached to said hetero oxygen atom. It should also be understood that the carbocyclic rings in dibenzofuran and its derivatives may be partially saturated so long as the heterocyclic ring oxide contains unsaturation at each of the carbon atoms attached to said hetero oxygen atom.

The derivatives of dibenzofuran for the process of this invention may be represented by the formula ##SPC2##

Where n is an integer from 0 to 2, m is an integer from 1 to 2, and each R may be selected from cycloalkyl of 5 to 7 carbon atoms, alkylated cycloalkyl of 6 to 11 carbon atoms, phenyl, benzylphenyl, diphenylyl alkylated phenyl of 7 to 19 carbon atoms, naphthyl and alkylated naphthyl of 11 to 14 carbon atoms.

The following substituents are illustrative of those which may be represented by R; cyclopentyl, cyclohexyl, cycloheptyl, 2-ethylcyclohexyl, 2-ethylcyclopentyl, 3-propylcycloheptyl, 1-methyl-2-ethylcyclohexyl, phenyl, benzylphenyl, diphenylyl, tolyl, ethylphenyl, isopropylphenyl, n-hexylphenol, 3-methyl-hexylphenyl, cumyl, 2,6-diisopropylphenol, 1-naphthyl, 2-naphthyl, methylnaphthyl, ethylnaphthyl, t-butylnaphthyl, dimethylnaphthyl or the like.

It should be noted that, in addition to the R substituents, the carbocyclic rings may contain a lower alkyl substituent straight chain or branched such as methyl, ethyl, propyl, isopropyl, butyl or an oxygen containing substituent such as hydroxyl, carbanol, aldehyde, carboxylic acid and the like.

R may also represent the addition of a 4 carbon chain in such a manner as to effect the formation of a benzenoid type fused ring structure giving rise to such compounds as dinaphthofurans, benzonaphthofurans and substituted derivatives thereof.

It will also, therefore, be understood that Group VIII elements used in the process of the present invention for preparing orthophenylphenol and its derivatives shall include one or more of the following named elements: platinum, palladium. iridium, osmium, rhodium, ruthenium, nickel, iron, and cobalt.

Orthophenylphenol and its derivatives are useful for the preparation of dyestuffs, for example 2,2'-dihydroxydiphenyl which is described in U.S. Pat. No. 3,169,149. Orthophenylphenol is also useful as an antimicrobial agent, for example, as a fungicide for the postharvest treatment of citrus fruit [McCornack, Proc. Fla. State Hort. Soc., 83, 229- 32 (1970)], as a biocidal agent or preservative for wood chips (U.S. Pat. No. 3,481,686), or admixed with other phenolics for the preparation of synthetic detergent-disinfectant or germicidal agents (U.S. Pat. No. 3,824,190).

Addition of hydrogen to furan compounds may proceed by way of a hydrogenation reaction to produce partially saturated or saturated compounds and by way of a hydrogenolysis reaction which involves cleavage of the carbon-oxygen bond or bonds and cleavage of carbon-carbon bonds. The prior art is replete with examples of both types of reactions using both catalytic and noncatalytic systems. Consequently it is obvious from the prior art that the hydrogenolysis reaction may be carried out in a facile manner for many of the furans, however, the prior art does not teach the hydrogenolysis of dibenzofuran, in particular, especially for the preparation of orthophenylphenol.

For example, a method for the cleavage of the furans at the carbon-oxygen bond is described in work done by Smith and Fuzek [J. Amer. Chem. Soc., 71, 415 (1949)] using a platinum catalyst in acetic acid solution in the presence of hydrogen. The reaction is carried out in a constant temperature water bath at low pressure. All the furans studied in this work are successfully cleaved using this method with the exception of dibenzofuran. The product of the reaction when dibenzofuran is used as a substrate involves the hydrogenation of both phenyl nuclei to give dicyclohexylene oxide. This is the only furan studied which does not cleave to a major extent.

Another method known in the art is the hydrogenolysis of dibenzofuran to give orthophenylphenol by way of reacting lithium metal with dibenzofuran in refluxing dioxane to form the lithium derivative of orthophenylphenol. followed by water-dioxane hydrolysis to give orthophenylphenol and other side products. This work was carried out by Gilman and Esmay [J. Amer. Chem. Soc., 20, 2947 (1953)]. Since the reaction of this process requires stoichiometric amounts of the alkali metal, the process cannot compete economically with the process of this invention.

The prior art as taught by Landa and co-workers [Sb. Vysoke Skoly Chem.-Technol. Praze, Technol. Paliv, 16, 159-70 (1969)] discloses that MoS₂ has been used as a catalyst for the hydrogenolysis of dibenzofuran to give orthophenylphenol. The reaction cited was carried out in a batch reactor charged with about 29 grams (0.17 moles) dibenzofuran and 4 grams MoS₂ having a surface area of 31 m² /gram. The reaction was allowed to continue for 30 minutes at 300° C and at a pressure that would be consistent with charging the reactor with 100 atmospheres of hydrogen gas at 17° C. The resulting product consisted of partially saturated and saturated derivatives of dibenzofuran as well as orthophenylphenol, the selectivity to orthophenylphenol product was only 33% at a conversion of 66%. A distinct advantage of the process of this invention over this prior art is the favorable selectivity of this invention to form orthophenylphenol.

The prior art according to Chandler and Sasse [Aust. J. Chem., 16, No. 1, 20 (1963)] teaches the use of Raney nickel for the hydrogenolysis of dibenzofuran by refluxing in methanol in the presence of hydrogen for about 16 hours. No orthophenylphenol is obtained. Instead, a partially saturated product is produced, namely phenylcyclohexanol. The disadvantage of this process, when compared to the process of this invention is the necessity of a dehydrogenation step in order to obtain the desired product of this invention. Thus Chandler and Sasse would require a two step process. The present invention teaches a viable one step process for the production of orthophenylphenol.

Likewise, Popa, Schwenk, and Ginsburg [J. Org. Chem., 16, 253 (1951)] carried out experimental work in which hydrogenolysis of the carbon-oxygen bond in furan compounds was brought about in the presence of nickel-aluminum alloy and aqueous alkali. These compounds yielded approximately equal amounts of two products, one resulting from the hydrogenation of the furan ring, the other a product of the hydrogenolysis of the furan ring. Of the furans tested, only dibenzofuran was substantially unreactive, i.e., only a small amount of phenolic material tentatively identified as orthophenylphenol was obtained. On the other hand, coumarilic acid, unlike dibenzofuran, gave good yields of its hydrogenolysis product β-(orthohydroxyphenyl)-propionic acid. Here again, as described in the work by Chandler and Sasse as well as Smith and Fuzek, little if any of the desired product is being formed in a one step reaction of the type described for the process of this invention.

Other approaches involving classical organic syntheses are described in the prior art, however the methods employed may result in the formation of the mixed isomers, i.e., ortho, para, and metaphenylphenol. This would not be desirable from the standpoint that of the three isomers formed, orthophenylphenol is the most effective as a biocidal agent. The other isomers, i.e., para- and metaphenylphenol, have been demonstrated to be biocidal agents with lesser degrees of effectiveness and, therefore, would only serve as diluents for this application. In addition the para and meta isomers would represent a product loss for the utility of the present invention, since the primary product desired is orthophenylphenol.

Application of Group VIII elements in the form of supported catalysts for the hydrogenolysis of simple furan structures, e.g., 2-methylfuran or 2-vinylfuran, is described in the art by Shuikin, Bel'skii, and Minachev, [J. General Chem. USSR, 29, 2932 (1959)]. For example, the hydrogenolysis of 2-methylfuran is carried out in the vapor phase at 275° C in the presence of a platinum on carbon catalyst and hydrogen to give a substantial amount of methylpropyl ketone product. Here again, however, only simple furan compounds were successfully cleaved at the carbon-oxygen bond.

It has now been found that control of conditions is important, i.e, rising temperature favors the hydrogenolysis reaction, while decreasing temperature favors the hydrogenation reaction. Likewise the pressure may serve an important function in the reaction. Most importantly, for the process of this invention, is the ability to select a combination of catalyst and conditions that will selectively cleave the furan ring in dibenzofuran and its derivatives at the carbon to oxygen linkage without substantially hydrogenating the unsaturated portion of the structure or without cleaving the phenyl to phenyl linkage previously designated as the bond between carbons 9 a and 9b.

It is, therefore, an object of the present invention to overcome the above disadvantages and thus provide an improved and more economical and commercially feasible hydrogenolysis process for the production of orthophenylphenol and its derivatives from dibenzofuran and its derivatives.

Another object of this invention is to provide a catalyst system for a viable one step hydrogenolysis process for the production of orthophenylphenol and its derivatives from dibenzofuran and its derivatives.

Another object of this invention is to provide a reactive, yet stable hydrogenolysis catalyst system that may be operated selectively to produce high yield of the preferred orthophenylphenol product.

These and other objects of the present invention will become apparent to those skilled in the art from the accompanying description and disclosure.

SUMMARY OF THE INVENTION

The process of this invention may be carried out in either the vapor phase or liquid phase, but preferably carried out under conditions in which the dibenzofuran and its derivatives are in the vapor phase. The temperature for this process may be in the range of about 260° to 500° C, but preferably about 300° to 500° C, or still more preferably from 350° to 475° C. At temperatures below about 260° C the undesirable hydrogenation reaction may occur and above about 500° C the catalyst life may be decreased. More particularly the process of this invention may be carried out at a pressure in the range of about 0.1 to 140 atmospheres, wherein the gas hourly space velocity (GHSV) is controlled to operate in the range of about 1 hr⁻ ¹ to 10,000 hr⁻ ¹ or higher, but preferably in the range of about 10 hr⁻ ¹ to 5,000 hr⁻ ¹. The molar ratio of hydrogen to dibenzofuran feed may be in the range of about 0.5:1 to 100:1. The process is carried out in the presence of a catalyst comprised of one or more of the Group VIII elements. Preferably the catalyst contains a minor amount of Group VIII element, that is, in the range of about 0.01 to 49% by weight and may be supported on a porous support. However, if consideration is given to the cost of certain Group VIII elements, it is immediately recognized that a more preferable range for certain of the Group VIII elements may be about 0.01 to 5% by weight. It is also however, within the scope of this invention that the Group VIII element may be used as an unsupported catalyst, and that said catalyst may be comprised of Group VIII element in the range of about 0.01 to 100% by weight, for example, as a metal gauze or honeycomb structure or as an insoluble compound such as the sulfide or oxide. The conditions and catalyst for the process of this invention may be selected to advantageously promote selective hydrogenolysis of dibenzofuran to form orthophenylphenol.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred catalyst for the process of this invention is comprised of minor amounts of one or more Group VIII elements, in the range of about 0.01 to 49% by weight, and more preferably, with cost consideration for certain of the Group VIII elements, in the range of about 0.01 to 5% by weight, and may be on a support which is in the form of powders, granules, spheres, tablets, extrudates, and other forms thereof. It may be prepared for example by impregnating a porous support with a compound of a Group VIII element which is subsequently decomposed. Depending on the type of decomposition carried out for the compound, the active may be in one or more possible forms, for example, as an oxide, sulfide, hydride, or the zero valent metal.

Carbon can be used as a porous support for the catalyst and may be obtained from any suitable source whether animal, vegetable, or mineral. A suitable carbon for example, may be obtained from mineral sources, particularly from a brownish black coal, intermediate between peat and bituminous coal, commonly referred to by those skilled in the art as lignite. It will be readily appreciated by those skilled in the art of catalysis that the carbon have adequate absorptive powers, for this reason the carbon should preferably be activated. It may be activated by any suitable means, for instance, by a thermal oxidation such as steam treatment of the lignite. An example of a carbon obtained by activation from lignite is Darco 12×20 supplied by Atlas Chemical Industries, Inc.

Other porous supports may be used as the catalyst carrier for the process of this invention, such as magnesia, alumina, silica, titania, or the like and mixtures thereof.

These porous supports may be obtained from any suitable source that will provide a material having the desired purity. These catalyst carriers should be substantially free from substances or metals that are known or may prove to be poisons for the catalyst of this invention.

The surface area for these catalyst carriers may be in the range of about 1 to 10,000 m² /gram or higher, or preferably about 10 to 2,000 m² /gram.

A catalyst may typically be prepared, using the following method. An impregnation solution comprised of an appropriate amount of soluble Group VIII metal compound dissolved in distilled water, or other suitable solvent, and diluted to the desired volume, preferably in excess of the solution absorptivity of the support. The support is intermingled with said solution and the resulting mixture is stirred for about five minutes at ambient conditions followed by slow removal of water by stirring and passing a soft air flow over the preparation to give a free-flowing material. Further drying may be accomplished by mild heating. The still damp preparation is finally dried over a period of about 18 hours at about 120° C in a forced air oven.

The dried preparation may be reduced by any suitable method, for example, reduced in hydrogen gas at about 450° C for about 4 hours or chemically reduced using an aqueous formaldehyde-KOH solution. The latter reduction method may require an additional step of base neutralization, water washing, and drying before the catalyst is used. If desired, the catalyst may be reduced in situ after being charged to the reactor.

According to a preferred feature of the invention, the catalyst is contacted during the reaction with the dibenzofuran, at the same time the catalyst is contacted during the reaction with a gas stream comprised of hydrogen or hydrogen mixed with water vapor or an inert gas such as nitrogen, argon, or helium. The gases and dibenzofuran may be preheated to reaction temperature prior to being introduced into the reactor containing the heated catalyst and said gases and dibenzofuran may be brought into contact with the catalyst by either upward or downward flow through the catalyst bed. The reactor effluent stream containing the orthophenylphenol product may be recycled back through the reactor or may be withdrawn continuously, followed by a product separation and subsequent recycle of the unreacted substrate if desired. The temperature of the reactor may be controlled by conventional means to maintain the desired operating condition.

After a period of operation when the catalyst may become deactivated by the presence of carbonaceous deposits, the catalyst may be reactivated or regenerated by passing an oxygen containing gas, for example air, air mixed with nitrogen, or air mixed with steam, into contact with the catalyst at an elevated temperature in order to burn the carbonaceous deposits from the catalyst. The method of regenerating the catalyst will depend on whether there is a fixed bed, moving bed, or fluidized bed operation. Regeneration methods and conditions are well known in the art.

The above described regeneration method would not apply to those catalysts comprised of a Group VIII element on a carbonaceous support, however it is known to those skilled in the art that a carbonaceous supported catalyst may also be regenerated by other methods such as by using chemical techniques, e.g. by extraction with a solvent such as benzene.

Also taught in this invention is that the reaction may be carried out in the liquid phase. For example, in a batch reactor the catalyst may be intermingled with dibenzofuran and hydrogen gas at a temperature in the range of about 350° to 500° C, but preferably about 400° to 450° C, and at a pressure of about 70 atm. or broadly from 3 to 200 atm., for a period of about 6 hours. A suitable solvent may be used if desired, a suitable solvent, for example, may be biphenyl, 1-methylnaphthalene, or dibenzofuran itself. Conventional methods of agitation for batch reactors may be used, such as rotating, rocking, or stirring. The reaction product may be separated from the catalyst by way of a built-in filter at the exit of the reactor, leaving said catalyst behind in the reactor for yet another reaction. Although the conditions cited herein for the liquid phase reaction are typical of those used for this type reaction, it is not intended that these conditions should limit the scope in practicing this invention.

The crude orthophenylphenol product produced in either continuous or batch operation or by liquid or vapor phase may be purified, for example, by distillation or caustic-extraction to remove the unreacted dibenzofuran and impurities therefrom.

The following examples illustrate the preparation of orthophenylphenol according to the present invention.

EXAMPLE 1

This example demonstrates that the reaction may be carried out in a vapor phase reactor, a preferred embodiment for the process of this invention, to form orthophenylphenol by hydrogenolysis of dibenzofuran.

A feed consisting of about 7.3:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 0.1% by weight platinum on alumina, the feed being in the vapor phase at a reaction temperature of about 400° C and pressure of about 7 atm, and at a total gas hourly space velocity of about 1100 hr⁻ ¹. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      60                                                           Orthophenylphenol 35                                                           Others             5                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 87% based on a 40% conversion of the total dibenzofuran present. Saturated products due to a hydrogenation reaction are not found.

EXAMPLE 2

This example demonstrates that the reaction may be carried out in the liquid phase in a batch type reactor.

A batch reactor is charged with the following: 106 g dibenzofuran, 38 g biphenyl to be used as solvent, 16 g of a catalyst comprised of about 1% by weight platinum on powdered carbon said weight of catalyst also consisting of about 64% by weight water. The reactor is pressured with hydrogen gas to a total pressure of about 70 atm (partial pressure of hydrogen about 54 atm) at the reaction temperature of about 475° C. The reaction is carried out at constant pressure for about 6.5 hours. The reaction products are discharged by forming a solution with toluene, as solvent and are analyzed by gas chromatography. The product contains the following corrected for the biphenyl solvent:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      82                                                           Orthophenylphenol 16                                                           Others             2                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 89%.

EXAMPLE 3

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 5% by weight platinum on carbon.

A feed consisting of hydrogen and dibenzofuran at a molar ratio of about 1:1 is brought in contact with about 15 cc total volume of said catalyst, the feed being in the vapor phase at a reaction temperature of about 405° C and at a flow rate of about 20 cc/minute. The reaction product is dissolved in toluene and analyzed by gas chromatography. The product distribution for this example indicates a good selectivity to the formation of orthophenylphenol. It is contemplated that within the scope of this invention a catalyst having elemental platinum as the major component, such as platinum gauze, may also be used as a catalyst for the reaction described in this example.

EXAMPLE 4

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 5% by weight ruthenium on carbon.

A feed consisting of hydrogen and dibenzofuran at a molar ratio of about 1:1 is brought in contact with about 15cc total volume of said catalyst, the feed being in the vapor phase at a reaction temperature of about 405° C and at a flow rate of about 20 cc/minute. The reaction product is dissolved in toluene and analyzed by gas chromatography. The product distribution for this example indicates a good selectivity to the formation of orthophenylphenol.

EXAMPLE 5

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 5% by weight osmium on carbon.

A feed consisting of hydrogen and dibenzofuran at a molar ratio of about 1:1 is brought in contact with about 15 cc total volume of said catalyst, the feed being in the vapor phase at a reaction temperature of about 400° C and at a flow rate of about 20 cc/minute. The reaction product is dissolved in toluene and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      95                                                           Orthophenylphenol 4                                                            Others            1                                                            ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 80%.

EXAMPLE 6

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 1% by weight palladium on an alumina.

A feed consisting of about 4:1 molar ratio of hydrogen to dibenzofuran is brought in contact with said catalyst, the feed being in the vapor phase at a reaction temperature of about 360° C and at a total gas hourly space velocity of about 420 hr⁻ ¹. The reaction product is dissolved in pyridine and analyzed by gas chromatography. Orthophenylphenol is formed with good selectivity in this reaction.

EXAMPLE 7

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of iron sulfide.

A batch reactor is charged with the following: 144g dibenzofuran, 26g of a catalyst comprised of iron sulfide. The reactor is pressured with hydrogen gas to a total pressure of about 54 atm (partial pressure of hydrogen about 41 atm) at the reaction temperature of about 475° C. The reaction is carried out at constant pressure for about 11.5 hrs. The reactor is discharged by forming a solution with an appropriate solvent, such as toluene, and the resulting solution is analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      90                                                           Orthophenylphenol 8                                                            Others            8                                                            ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 80%.

EXAMPLE 8

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 5% by weight iridium on a carbon.

A batch reactor is charged with the following: 115 g dibenzofuran, 1 g of a catalyst comprised of about 5% iridium on a powdered carbon support. The reactor is pressured with hydrogen gas to a total pressure of about 70 atm (partial pressure of hydrogen about 54 atm) at the reaction temperature of about 450° C. The reaction is carried out at constant pressure for about 24 hours. The reactor is discharged with toluene solvent and the resulting solution is analyzed by gas chromatography. The product distribution for this example indicates a good selectivity to the formation of orthophenylphenol. Other products formed are comprised of compounds having molecular weight greater than orthophenylphenol.

EXAMPLE 9

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 39% by weight cobalt on silica.

A feed consisting of about 4:1 molar ratio of hydrogen to dibenzofuran is brought in contact with said catalyst, the feed being in the vapor phase at a reaction temperature of about 370° C and at a total gas hourly space velocity of about 420 hr⁻ ¹. The reaction product is dissolved in an appropriate solvent, such as pyridine, and analyzed by gas chromatography. The solution contains product with a good selectivity to formation of orthophenylphenol at a low conversion of dibenzofuran.

EXAMPLE 10

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 1% by weight rhodium on alumina.

A feed consisting of about 16:1 molar ratio of hydrogen to dibenzofuran is brought in contact with said catalyst, the feed being in the vapor phase at a reaction temperature of about 305° C and at a total gas hourly space velocity of about 1325 hr⁻ ¹. The reaction product is dissolved in an appropriate solvent, such as pyridine, and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      84                                                           Orthophenylphenol 12                                                           Others             4                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 75%.

EXAMPLE 11

This example demonstrates that the reaction may be carried out in the presence of a catalyst comprised of about 36% by weight nickel on a porous support. This catalyst is available from a commercial source, i.e., Girdler G-52 catalyst from Girdler Chemical, Inc.

A partial oxidation of the nickel is carried out by the catalyst manufacturer in order to stabilize the catalyst for safe transport. An in situ reduction of the catalyst is performed in the reactor prior to the reaction being carried out.

A feed consisting of about 30:1 molar ratio of hydrogen to dibenzofuran is brought in contact with said catalyst in the vapor phase at a reaction temperature of about 305° C and at a total gas hourly space velocity of 1325 hr⁻ ¹. The reaction product is dissolved in an appropriate solvent, such as pyridine, and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      93                                                           Orthophenylphenol 6                                                            Others            1                                                            ______________________________________                                    

Selectivity to formation of the othophenylphenol product is about 85%.

EXAMPLE 12

This example demonstrates that when the reaction is carried out at reaction temperatures below the preferred range for the process of this invention described hereinabove, saturated forms of the desired product orthophenylphenol may result.

A feed comprised of hydrogen gas fed at a rate of about 80 cc/minute and dibenzofuran fed at a rate of about 0.08 g/minute is brought in contact with a catalyst comprised of about 0.5% by weight platinum on alumina, the feed being in the vapor phase at a reaction temperature of about 260° C, but nearly liquid phase since the boiling point of dibenzofuran is about 285° C. The total gas hourly space velocity for this reaction is about 400 hrs⁻ ¹. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      72                                                           Orthophenylphenol 17                                                           Others            11                                                           ______________________________________                                    

Selectivity to formation of the desired orthophenylphenol product is about 61%. A major portion of the others product is in the form of saturates, such as cyclohexylphenol, phenylcyclohexanol, cyclohexylcyclohexanol, and dicyclohexylene oxide, representing a substantial selectivity loss. An additional dehydrogenation step is required to recover the saturated forms as product.

EXAMPLE 13

This example demonstrates that the reaction may be carried out at a reactor pressure that is essentially atmospheric pressure.

A feed consisting of about 10:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 1% by weight platinum on alumina, the feed being in the vapor phase at a reaction temperature of about 305° C, and at a total gas hourly space velocity of about 1400 hr⁻ ¹. The reactor is operated at atmospheric pressure. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      83                                                           Orthophenylphenol 13                                                           Others             4                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 76% based on 18% conversion of the dibenzofuran. Saturated products due to a hydrogenation reaction are not found.

EXAMPLE 14

This example further demonstrates that the reaction may be carried out at a reactor pressure that is essentially atmospheric pressure.

A feed consisting of about 36:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 1% by weight rhodium on an alumina, the feed being in the vapor phase at a reaction temperature of about 305° C, and at a total gas hourly space velocity of about 2600 hr⁻ ¹. The reactor is operated at atmospheric pressure. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      85                                                           Orthophenylphenol 12                                                           Others             3                                                           ______________________________________                                    

Selectivity to the formation orthophenylphenol product is about 80% based on 15% conversion of the dibenzofuran.

EXAMPLE 15

This example demonstrates that the reaction may be carried out at a reactor pressure of about 8 atm.

A feed consisting of about 6:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 0.5% by weight palladium on magnesia, the feed being in the vapor phase at a reaction temperature of about 400° C, and at a total gas hourly space velocity of about 600 hr⁻ ¹. The reactor is operated at a pressure of about 8 atm. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      75                                                           Orthophenylphenol 23                                                           Others             2                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is 92% at a 25% conversion of the dibenzofuran.

EXAMPLE 16

This example demonstrates that the reaction may be carried out at a reactor pressure of about 70 atm.

A batch reactor is charged with the following: 106 g dibenzofuran, 38 g biphenyl to be used as a solvent, 16 g of a catalyst comprised of about 1% by weight platinum on powdered charcoal, said weight of catalyst also consisting of about 64% by weight water. The reactor is pressured with hydrogen gas to a total pressure of about 70 atm (partial pressure of hydrogen about 54 atm) at the reaction temperature of about 475° C. The reaction is carried out at constant pressure for about 6.5 hours. The reaction products are discharged by forming a solution with toluene as solvent and are analyzed by gas chromatography. The product contains the following corrected for the biphenyl solvent:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      82                                                           Orthophenylphenol 16                                                           Others             2                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 89%.

EXAMPLES 17-22

The following examples demonstrate that the hydrogen to dibenzofuran (H₂ :DBF) molar ratio and the gas hourly space velocity (GHSV) may be varied according to the preferred embodiment for the process of this invention described hereinabove for the preparation of orthophenylphenol (OPP) from dibenzofuran. It should be understood that for complete hydrogenolysis a molar ratio of 1:1 for hydrogen to dibenzofuran satisfies the stoichiometry of the reaction for the process of this invention.

Examples are carried out in a vapor phase reactor whereby a feed consisting of hydrogen and dibenzofuran is brought in contact with a catalyst, the feed being in the vapor phase at reaction temperature, and at a specified gas hourly space velocity. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The catalyst, conditions, and results for each example are described in the following table.

    __________________________________________________________________________           CATALYST     TEMP.                                                                               TOTAL GHSV                                                                            H.sub.2 :DBF                                                                           CONVERSION                                                                            SELECTIVITY TO                   EXAMPLE                                                                              TYPE         (° C)                                                                        (HR.sup.-.sup.1)                                                                      MOLAR RATIO                                                                            (%)    OPP(%)                           __________________________________________________________________________     17    1% Pt/Alumina                                                                               305   225   0.7     12     85                               18    1% pt/Alumina                                                                               305  1300   27      30     65                               19    1% Rh/Alumina                                                                               305  2600   36      15     77                               20    0.5% Pt + 0.5% Pd/Alumina                                                                   305  1300   64      14     42                               21    0.5% Pd/Magnesia                                                                            400   10    6       56     71                               22    0.5% Pt/Alumina                                                                             400   600   7.3     65     71                               __________________________________________________________________________      The major byproduct formed in these reactions is biphenyl.               

EXAMPLE 23

Repeat of Example 1 of this invention.

This example demonstrates that the reaction may be carried out in the presence of a catalyst prepared from a support material comprised of alumina.

EXAMPLE 24

Repeat of Example 2 of this invention.

This example demonstrates that the reaction may be carried out in the presence of a catalyst prepared from a support material comprised of carbon.

EXAMPLE 25

Repeat of Example 3 of this invention.

This example demonstrates that the reaction may be carried out in the presence of a catalyst prepared from a support material comprised of silica.

EXAMPLE 26

Repeat of Example 15 of this invention.

This example demonstrates that the reaction may be carried out in the presence of a catalyst prepared from a support material comprised of magnesia.

EXAMPLE 27

This example demonstrates that the reaction may be carried out in the presence of a catalyst prepared from a support material comprised of titania.

A feed consisting of about 6:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 0.5% by weight palladium on titania, the feed being in the vapor phase at a reaction temperature of about 430° C, and at a total gas hourly space velocity of about 550 hr⁻ ¹. The reaction product is dissolved in pyridine and analyzed by gas chromatography. The product distribution for this example indicates a good selectivity to the formation of orthophenylphenol.

EXAMPLE 28

This example demonstrates catalyst stability for the process of this invention.

A feed consisting of about 7.3:1 molar ratio of hydrogen to dibenzofuran is brought in contact with a catalyst comprised of about 0.1% platinum on alumina, the feed being in the vapor phase at a reaction temperature of about 400° C and pressure of about 7 atm, and at a total gas hourly space velocity of about 1100 hr⁻ ¹. After about 17.5 hours total run time a sample of the reaction product is dissolved in pyridine and analyzed by gas chromatography. The product contains the following:

    ______________________________________                                                         Wt. Percent                                                    ______________________________________                                         Dibenzofuran      76                                                           Orthophenylphenol 21                                                           Others             3                                                           ______________________________________                                    

Selectivity to formation of the orthophenylphenol product is about 89% at a 24% conversion of the total dibenzofuran present. Biphenyl is the major constituent of the others product. Saturated products due to a hydrogenation reaction are not found.

EXAMPLE 29

After a period of operation of 16 hours at the conditions described in Example 22 of this invention, the feeding of dibenzofuran and hydrogen is stopped, and the catalyst is regenerated for a period of 6 hours at 450° C, using a gas stream comprised of 2.1 vol. % oxygen. The catalyst temperature is then adjusted to 400° C, flow of the regeneration gas is stopped, and the catalyst is reduced in flowing hydrogen for a period of 1 hour.

The reaction conditions of Example 22 are again repeated. After a period of time the reaction product is analyzed by gas chromatography, and is found to contain 43.2% by weight of orthophenylphenol.

It should be apparent that the particular embodiments chosen to illustrate the invention are not all inclusive and that many changes and variations could be made therein, some of which for example depend upon the activity of the particular catalyst and upon the nature of the starting material. All such changes, modifications, variations or the like, however, which will be apparent to those skilled in the art after considering this disclosure and which do not depart from the spirit and scope of the invention are deemed to be covered by the subjoined claims. 

What is claimed is:
 1. Process for the production of orthophenylphenol and substituted ortho-phenylphenols which comprises contacting dibenzofuran or a substituted dibenzofuran of the formula ##SPC3##where n is an integer from 0 to 2, n is an integer from 1 to 2, and each R may be selected from the group consisting of lower alkyl, cycloalkyl of 5 to 7 carbon atoms, alkylated cycloalkyl of 6 to 11 carbon atoms, phenyl, benzylphenyl, diphenylyl, alkylated phenyl of 7 to 19 carbon atoms, naphthyl, alkylated naphthyl of 11 to 14 carbon atoms, hydroxyl, carbanol, aldehydo, carboxy and R may also represent the addition of a 4 carbon chain in such a manner as to form a benzoid type fused ring structure, in the presence of hydrogen, at a temperature of from 260° to 500° C., in the presence of a catalyst consisting essentially of a Group VIII element.
 2. Process as in claim 1, in which the process is conducted in the vapor phase, at a gas hourly space velocity of from 1 hr⁻ ¹ to 10,000 hr⁻ ¹.
 3. Process as in claim 1 in which the process is conducted in the vapor phase at a gas hourly space velocity of from 1 hr⁻ ¹ to 10,000 hr⁻ ¹, and the Group VIII element is on a porous support.
 4. Process as in claim 1 in which is conducted in the liquid phase in the presence of hydrogen at a hydrogen proportion of from 0.5:1 to 100:1 moles of hydrogen per mol of feedstock.
 5. The process of claim 1 wherein the reaction is carried out in the vapor phase at a temperature of from 300° to 500° C. at a gas hourly space velocity of from 10 hr⁻ ¹ to 5,000 hr⁻ ¹, in the presence of hydrogen at a molar ratio of hydrogen to the dibenzofuran feedstock in the range of 0.5:1 to 100:1.
 6. Process as in claim 5 in which the pressure is from 1 to 100 atmospheres.
 7. Process as in claim 5 in which the Group VIII element is platinum on carbon.
 8. Process as in claim 5 in which the Group VIII element is platinum on alumina.
 9. Process as in claim 5 in which the Group VIII elements are platinum and palladium on alumina.
 10. Process as in claim 5 in which the Group VIII element is ruthenium on carbon.
 11. Process as in claim 5 in which the Group VIII element is osmium on carbon.
 12. Process as in claim 5 in which the Group VIII element is palladium on alumina.
 13. Process as in claim 5 in which the Group VIII element is iron sulfide.
 14. Process as in claim 5 in which the Group VIII element is iridium on carbon.
 15. Process as in claim 5 in which the Group VIII element is cobalt on silica.
 16. Process as in claim 5 in which the Group VIII element is rhodium on alumina.
 17. Process as in claim 5 in which the Group VIII element is nickel on silica-alumina.
 18. Process as in claim 5 in which the catalyst is regenerated by contacting the catalyst with an oxygen containing gas at a temperature of from 300° to 700° C, and is then reduced at a temperature of 300° to 550° C.
 19. Process for the preparation of orthophenylphenol which comprises contacting dibenzofuran at a temperature of from 260° to 500° C in the presence of a catalyst consisting essentially of a Group VIII element. 